Annual acres burned has grown from ~1 M acres in 1984 to over 10M acres in 2020.

Click the play button at the lower right to see the trend.

This is not news for anyone in the fire business. What is not captured here are the lives impacted, structures destroyed, habitats fundamentally altered (often beyond what fires would naturally do because of unnatural fuels buildup) and resources used in suppression.

Question: how do you think this compares to what would have burned in the years just prior to European colonization?

Data for the lower 48 United States from the Monitoring Trends in Burn Severity program (https://www.mtbs.gov/).

There was ~172,000,000 acres of fire annually prior to European colonization

Prior to European colonization most of the fires were located in the central and eastern regions, and were most common in the grassland ecosystems, where replacement fires could have happened every 1-3 years. The pine, oak and hickory forests of the east (especially the longleaf pine ecosystems of the southeast) would typically have surface fires every 5-10 years, with replacement fires being rare.

Hover over a state to get historical percentage burned annually by fire type.

• Surface fire = 0-25% top kill
• Mixed fire = 26-75% top kill
• Replacement fire = 76-100% top kill

Fire severity varied by ecosystem type

Ecosystems have varying levels of different fire types (aka severity; surface, mixed or replacement).

Hover over chart to follow patterns.

It’s important to explore conversion as fire not only works differently from ecosystem to ecosystem, but also on developed and urban lands. By hovering over the red Agricultural band on the right you can see that our farmlands were mostly grasslands and hardwoods historically. Hover over the blue Grassland (past) band and you’ll see what those lands are today, noting that roughly 93M acres of former grasslands are now classified as shrublands.

If we were to have fires at historical rates today, not including agriculture and urban lands, we’d have more than 100 M acres per year.

• Sagebrush intermountain basins story
• Alaska
• What if we looked at maximum fire years?